There was an awful lot riding on the slender shoulders of those seven kids in the self-styled Losers Club. Not only did the heroes of "IT" have to save the town of Derry, Maine from Pennywise the Clown, but they also had to save the box office from its worst summer in over a decade. Analysts gave the much-anticipated Stephen King adaptation a good shot, predicting it might earn around $60 million this weekend.

Turns out they were wrong. The predictions were off, by nearly 100 percent.

In fact, Sunday estimates have "IT" raking in $117.2 million. The movie broke all sorts of records. Among them: biggest September opening ever, biggest three-day weekend for a horror film, and biggest opening day for a horror film ($51 million). Its Thursday night preview take of $13.5 million marks the biggest preview for an R-rated movie, a horror film, and a September release. It's the third biggest opening weekend of 2017 and the second biggest R-rated opening of all time, after "Deadpool" (which debuted with $132.4 million).

We'd ask how the experts so vastly underestimated the potential of "IT," but then, Hollywood's conventional wisdom has been off about nearly everything this summer. Here are some of the rewritten rules that "IT" has let fly like so many red balloons.

Now comes "IT," based on a familiar 1990 mini-series. Hardly original, but many people knew and loved the story and wanted to see it done well on a big screen. It was well-marketed, with a frightening trailer that lit up YouTube, with 197 million views in its first 24 hours. Anticipation was high, especially after a summer of disappointments. So the box office was primed for "IT" to succeed.

2. It's Fresh

The negative power of the movie review aggregator's green splat icon has been another Hollywood complaint all summer. Of course, some poorly reviewed films succeeded anyway ("The Emoji Movie") while many critical favorites did not. "IT" wasn't a great test case, in that horror movies are usually critic-proof anyway. But "IT" did get mostly good reviews (86 percent fresh at RT), so at least ticket buyers saw the film as a safe investment. Plus, Warner Bros.' New Line unit was happy to let reviews run early, knowing that they'd be positive and would combine to make a high RT score. So the studios aren't above emphasizing RT for marketing purposes when it works to their advantage.

3. Stephen King Rules

In this case, the stars weren't the mostly anonymous cast or even director Andy Muschietti, a name only to horror fans who remember his hit "Mama" from four and a half years ago. Rather, the star is King, who's been a reliable box office draw for 40 years... up to a point. Remember, just a month ago, the adaptation of his "Dark Tower" saga flopped. But that was a film that hardcore King fans found disappointingly unfaithful to the novels and regular moviegoers simply found baffling. King sells tickets, but only for the right titles, properly executed.

4. IMAX Was Big

"IT" might not have done as well had it been released a month ago. That's because fellow Warners release "Dunkirk" was hogging all the IMAX screens. Now, however, it was able to grab 377 of those giant screens, marking the largest September IMAX release ever. And those surcharges resulted in $7.2 million of "IT"'s take coming from IMAX, also a September record.

5. The Netflix Effect

The streaming service is yet another supposed digital killer of theatrical sales. Even so, it couldn't have hurt that one of Netflix's most popular shows of the past year was "Stranger Things," an '80s nostalgia piece that owes a huge debt to King's books and movies, "IT" in particular. So Netflix would actually have helped build up anticipation for a movie that went straight to the source that had inspired "Stranger Things."

6. Hurricanes Couldn't Stop "IT"

Florida generally accounts for some 6 percent of the box office, so it was widely assumed that Hurricane Irma would put a large dent in sales this weekend. Plus, many Houston screens were expected to remain dark in the aftermath of Hurricane Harvey last week. Nonetheless, some theaters in central Florida remained open. And evacuees who made it to other states may have chosen to ride out the storm watching escapist fare at the multiplex. So the storms' effects were minimal, as was apparent from all the box office records "IT" broke.

7. If You Build It, They Will Come

Overall, the "Field of Dreams" rule remains in effect. If you make a movie that people actually want to see, they'll happily show up at the multiplex and buy tickets. Whether or not it's a familiar title, whether it earns a high or low score at Rotten Tomatoes, whether or not it's made by A-list actors and directors, and whether or not there are outside factors discouraging people from going to the movies, what matters most is execution.

Seven young outcasts in Derry, Maine, are about to face their worst nightmare -- an ancient, shape-shifting evil that emerges from the sewer every 27 years to prey on the town's children. Banding together over the course of one horrifying summer, the friends must overcome their own personal fears to battle the murderous, bloodthirsty clown known as Pennywise. Read More